The present invention relates to an improved mesh tray assembly useful for holding small, delicate articles such as contact lenses or intraocular lenses during extraction, hydration and/or coating/deposition processes.
In a typical process for the manufacture of polymeric lenses, a composition containing a diluent and suitable monomers is charged to a mold and cured. The molded lens can be subjected to machining operations such as lathe cutting, buffing, and polishing and further subjected to extraction, hydration, and sterilization procedures. Depending on the polymeric material used to produce the lens, additional processing such as surface coating or plasma deposition may help render the finished lens more comfortable.
Generally, in the manufacture of lenses, the monomer mixture does not completely polymerize. These unreacted monomers, or partially reacted oligomers remain in the lens matrix and need to be removed. Additionally, additives from the mold may migrate into the lens material. Removal of these undesirable materials (herein referred to as xe2x80x9cextractablesxe2x80x9d) can be accomplished by extraction. Failure to perform an extraction step on a lens may cause eye irritation. The lens may also have reduced optical clarity which would require further surface treatment or coating. Additionally, there is concern with the possibility of ocular damage which may occur upon wearing an unextracted lens. The extraction of any lens contaminants must be as complete as possible.
Lenses to be extracted are typically placed in a chamber that allows fluid to be circulated about the lens but keeps the lens from inverting or folding over. It is desirable to process a plurality of lenses simultaneously.
Examples of extraction chambers can be seen in U.S. Pat. Nos. 5,080,839 and 5,094,609 (both to Kindt-Larsen). The plastic or metal chambers disclosed by Kindt-Larsen are comprised of male and female members. Solution flows into the formed chamber through centrally located lines in both male and female members. Drainage openings are located radially on the outer perimeter of the male member. Solution flow takes place on both surfaces of the lens in a radial direction surrounding the lens.
Lenses that undergo coating or surface treatment are also arranged on a fixture. One such device is disclosed in U.S. Pat. No. 5,874,127 (Winterton et al). The contact lens is supported by a plurality of point-contact support locations. The support locations are sufficient to support the lens to be treated but do not prevent uniform coating of the lens.
The present invention is directed to a tray assembly for handling small, delicate articles such as contact lenses or intraocular lenses during certain manufacturing process such as, e.g., extraction, hydration and/or coating processes.
In the process of removing extractables from contact lenses, the solvent needs to be able to flow freely around the lenses for maximum extraction efficiency. In addition, to achieve high productivity, it is necessary that the extraction be carried out on batches containing a multiplicity of lenses. These desirable features are provided by the tray assembly of the present invention. The mesh employed in the fabrication of the tray assembly permits unhampered circulation of the solvent around the lenses contained in the multi-well tray. The invention further provides for the arrangement of multiple tray assemblies for simultaneous extraction of large numbers of contact lens within a bath of solvent, resulting in even greater through-put efficiency in the extraction process.
The tray assembly includes either the combination of a mesh insert and a support tray or a tray comprised of mesh. The mesh insert may be comprised of a single sheet of flexible mesh or two separated portions. The first portion has a series of wells to hold the lenses while the second portion of the mesh sheet lies over the lenses, securing them in the wells. If the mesh insert is a single sheet, it is preferably with a living hinge separating first and second portions. The second portion is laid upon the first portion. The second portion may have slight depressions which align with the wells of the first portion.
The support tray is rigid and is comprised of top and bottom portions. In one embodiment, the bottom portion comprises a tray having a plurality of through-holes formed therein and aligned to accept the mesh insert wells. The top portion of the tray is a wire grid which is joined to the bottom portion of the tray by a hinge. After the mesh insert has been placed onto the bottom portion of the tray, the top portion is pivoted over the bottom portion of the tray and secured by a latch thereby sandwiching the mesh and lenses therebetween. The tray assembly, with an individual lens in each well, is now ready for processing.
Another embodiment of the support tray is also comprised of two separate top and bottom portions. The top and bottom of the support tray are both comprised of a wire-like grid with the bottom portion holding the mesh insert. The top tray portion removably attaches to the bottom tray portion, securing the mesh insert in place between the top and bottom portions of the support tray.
A further embodiment may include multiple mesh inserts and covers stacked on top of each other. In this embodiment, each mesh insert acts as a separate supporting tray. A central opening in each mesh insert allows a center shaft to be inserted so as to keep the mesh inserts stable and in position during the lens processing. The center shaft may have openings to facilitate solvent flow around the mesh inserts. After a predetermined number of mesh inserts and covers are stacked upon each other, a stack cover mesh is placed over the top mesh insert.
The tray assemblies may be any desirable shape or configuration. Additionally, the tray assemblies may be stacked upon each other or stacked in a separate holder.